I think for Frankfurt-Bochum you need to try
http://www.bahn.de/international/view/en/index.shtml
This is the site for the German railway (DB=Deutsche Bahn). Including long distance
trains. The VRR site I linked above is just for public transportation in the region where
Bochum lies (which is useful to get around in the area).
But I am not sure you can book tickets that much in advance...but if (or when) they've got
tickets they will offer 'normal fare' and 'savings fare'. The latter of course is cheaper, but
you have to catch exactly the train you are buying the ticket for. If you miss it, there are
no refunds. With the normal fare you can just take the next one. I usually get the cheaper
fare and pick a train which allows for some delay in plane arrival etc.. I might have to wait
some time but you save 50% or more...and that's a lot of beers (which you are allowed to
drink in public, btw

).
Customs/immigration definitely isn't as bad as in the States...
and the time you spend there also depends on the amount of smartass-ery you confront
those guys in the ridiculously colored uniforms with...